Sen. Rand Paul (R-Ky.) today filmed a TV ad in support of Congressional candidate Thomas Massie and plans to endorse him soon.

“I’ve made the decision today to go ahead and help him,” Paul said in an interview today in his Senate office. “I filmed an ad for him today.”

Massie, the Lewis County judge-executive, is locked in a competitive race for Kentucky’s open 4th district seat, currently occupied by retiring Rep. Geoff Davis (R). The other two top contenders in the race are state Rep. Alecia Webb-Edgington and Boone County Judge-Executive Gary Moore.

Paul said an official endorsement of Massie would come soon. “It’s not that I dislike the the other candidates. And I probably wouldn’t have gotten involved, but other people got involved endorsing one of the other candidates and so I felt, to level the playing field, I’m going to get involved,” he said.

Webb-Edgington, who has establishment GOP backing, got the endorsements of Davis and former Sen. Jim Bunning (R-Ky.) last month.

“Thomas Massie is an extraordinary candidate. You don’t get people like this,” Paul said, lauding the candidate’s biography as the “American dream” and praising his tenure as judge-executive.

“He ran, and within three months, he found enough savings to pay for his salary,” Paul said. “I think he’ll be one of the people up here who will be a believer in civil liberties and really will vote to cut the spending that’s necessary to balance the budget.”

In Paul’s contested 2010 primary against then-Secretary of State Trey Grayson, Massie supported Paul, while Webb-Edgington and Moore supported Grayson.

Republicans familiar with Kentucky politics think the Paul endorsement has the potential to push Massie to victory in the May 22 primary.

“Geoff Davis’ engagement in the race galvanized this narrative of establishment vs. tea party. And if you look at how Rand Paul did in northern Kentucky, it’s obvious that Paul can move people up there, and I think it will have an impact,” said one longtime GOP observer of Kentucky politics.

In other good news for Massie, a super PAC is spending more than a half-million dollars on TV advertising in favor of the tea-party-affiliated candidate. Liberty for All super PAC spent a whopping $543,000 Wednesday on advertising in support of Massie, according to Federal Election Commission filings.

The Louisville Courier-Journal reported that the super PAC “is funded largely by John Ramsey, a 21-year-old student at the University of Texas in Austin, who works along with his brother and sister managing investments left to them by their grandfather.”

The 4th district is safe Republican turf, so the winner of the primary is almost certain to come to Congress next year.